The statement that you identified correctly emphasizes that in a many-to-many relationship, the tables involved cannot be changed directly. This is because many-to-many relationships in databases are typically managed through a junction table that creates a bridge between the two tables. Altering the tables directly involved in a many-to-many relationship would disrupt this bridge, potentially leading to data integrity issues.
In a many-to-many relationship, one record in Table A can relate to multiple records in Table B, and one record in Table B can relate to multiple records in Table A. This complexity necessitates having a junction table that handles these connections. Changing the underlying tables without considering the junction table's structure would create inconsistencies in how data is related.
The context for the other options reinforces this understanding. In a one-to-many relationship, you have the flexibility to change the table on the "one" side or even the "many" side without disrupting the relationship's integrity. Similarly, in a many-to-one relationship – which is just the inverse perspective of one-to-many – table changes can be made as needed.
Thus, the uniqueness of the many-to-many relationship requires maintaining the established relationships through a junction table, making it impossible to change the associated tables without affecting data integrity.